Individual listings can be found in Bangkok's district articles
Bangkok boasts a stunning 50,000 places to eat; not only thousands of Thai restaurants, but a wide selection of world-class international cuisine too. Prices are generally high by Thai standards, but cheap by international standards; a good meal is unlikely to cost more than 300 baht, although there are a few restaurants (primarily in hotels) where you can easily spend 10 times this.
Sukhumvit by far has the best restaurants of Bangkok, though prices tend to be high. Practically every cuisine in the world is represented here, be it French, Lebanese, Mexican, Vietnamese, or fusion combining many of these together in a quirky, but delicious mix. Bangkok's Italian town is Soi Ton Son near Siam Square. Of course, for those on a budget, street stalls abound with simple Thai dishes at around 30 baht. There are especially plenty of budget restaurants in Khao San Road.
There are plenty of vegetarian restaurants in the more tourist-friendly parts of town (especially in hippie district Khao San Road). Vegetarian dishes are also readily available on the menus of regular restaurants. On request, even typical street restaurants will easily cook a vegetarian equivalent of a popular Thai dish for you. Ask for "jay" food to leave the meat out of the dish. For example, "khao pad" is fried rice and "khao pad jay" is vegetarian fried rice. For vegans, the most common animal product used would be oyster sauce. To avoid it, say "mai ao naam man hoi". Be aware that all street noodle vendors use animal broth for noodle soup.
Don't miss out on a cold ice cream in hot Bangkok. Dairy Queen and Swensen's has booths in many malls and shopping centres. Their ice creams are tasty, cheap and safe for westerners to eat.